Support links with lockable adjustment feature

ABSTRACT

A cam-type apparatus is included in a support link between outer and inner cases of gas turbine engines for centering the cases one to another. The cam-type apparatus is lockable to allow locking an adjusted position of the cam-type apparatus.

TECHNICAL FIELD

The application relates generally to a gas turbine engine and, moreparticularly, to a gas turbine engine having lockable adjustmentfeatures for support-links between annular outer and inner cases.

BACKGROUND OF THE ART

A turbofan gas turbine engine basically includes a core portion whichmust be mounted inside a bypass duct. A traditional engine mount systemfor a fuselage mount turbofan gas turbine engine reacts to thrust,lateral and vertical loads at the front mounting plane (on theintermediate case of the engine), and reacts to lateral and verticalloads at the rear mount. The rear mount is usually located either on thebypass duct, forming a cantilever core as schematically shown in FIG. 9,or on the engine core, typically near the turbine exhaust case, forminga rear core mount as schematically shown in FIG. 10. However, thecantilever core suffers from distortion due to inertia loads and tendsto droop from the burden of these loads, resulting in tip clearance losswhich is critical to the functioning of an axial compressor. The rearcore mount suffers from significant bending of the core portion causedby thrust loads. The rear mount carries a load due to a moment createdby the engine thrust line of action being offset from the thrustreaction plane. Thus, the core portion is loaded analogous to a simplysupported beam with a point moment located at the front mount plane.This effect is critical, particularly on an axial compressor, since themaximum deflection occurs at the rear compressor stages, where small tipclearances are needed to maintain engine operability.

Accordingly, there is a need to provide an improved mounting system forgas turbine engines.

SUMMARY

In one aspect, there is provided a support-link having lockableadjustment features for interconnecting an annular outer case and anannular inner case of a gas turbine engine, the annular inner case beingco-axially positioned within the annular outer case, the support linkcomprising: a plurality of rods having opposed inner and outer ends,each rod being connected at the outer end to the annular outer case andconnected at the inner end to the annular inner case; and a plurality oflockable adjusting devices for adjustably connecting the respective rodsto one of the annular outer and inner cases, each of the lockableadjusting devices including a pin and a connecting base attached to saidone of the outer and inner cases, the pin having a connecting sectionand a base section, the connecting section having a central axiseccentric to a central axis of the base section, the connecting sectionbeing received in a hole defined in one of the outer and inner ends ofone rod and the base section being received in a hole defined in theconnecting base, the pin being rotatable relative to the respective rodand connecting base in order to select an angular position of aneccentric distance between the central axes of the respective connectingsection and base section of the pin before the pin is locked in positionto secure the rod to the connecting base.

In a second aspect, there is provided a turbofan gas turbine enginecomprising: a core portion of the engine; an annular bypass duct wallcoaxially surrounding and supporting the core portion, thereby to definean annular bypass air passage radially between the core portion and thebypass duct for directing a bypass air flow passing therethrough; and asupport link interconnecting the core portion and the annular bypassduct wall, the support link including a cam-type apparatus adjustablefor centering the core portion with respect to the annular bypass ductwall, the cam-type apparatus being lockable to allow locking an adjustedposition of the cam-type apparatus, the cam-type apparatus being locatedoutside the annular bypass air passage while the support link extendsacross the annular bypass air passage.

Further details of these and other aspects of the present invention willbe apparent from the detailed description and drawings included below.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of a turbofan gas turbineengine as an exemplary application of the describe subject matter;

FIG. 2 is a perspective view of a rear mounting assembly according toone embodiment, as used in the engine of FIG. 1;

FIG. 3 is a partial perspective view of the rear mounting assembly ofFIG. 2 in an enlarged portion, showing one of the connecting bracketswith a mounting portion;

FIG. 4 is a partial perspective view of the circled area 4 of the rearmounting assembly of FIG. 2, looking into the inside surface of a bypassduct wall in an enlarged scale, showing the attachment of link rods tothe connecting brackets;

FIG. 5 is a cross-sectional view of the link rod taken along line 5-5 inFIG. 4, showing the aerodynamic profile of the link rod;

FIG. 6 is a partial perspective view (partially exploded) of the rearmounting assembly of FIG. 2 in an enlarged scale, showing a lockableadjustment device for connection of the link rods to a mid turbine frame(MTF) of a core portion of the engine;

FIG. 7 a is a top plan view of a pin used in the lockable adjustmentdevice of FIG. 6, showing an annular position of an eccentric distancebetween the central axes of the respective connecting section and basesection of the pin;

FIG. 7 b is a side elevational view of the pin in FIG. 7 a with aconnected inner end of a link rod shown in broken lines;

FIG. 8 is a perspective view of a lockable adjustment device accordingto another embodiment;

FIG. 9 is a schematic illustration of a prior art turbofan gas turbineengine mounting system, showing a cantilever core portion; and

FIG. 10 is a schematic illustration of a prior art turbofan gas turbineengine mounting system, showing a rear core portion mount.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 a long duct mixed flow (LDMF) turbofan gas turbineengine (not numbered) includes an annular bypass duct wall 10, a lowpressure spool assembly (not numbered) which includes a fan assembly 14,a low pressure compressor assembly (not shown) and a low pressureturbine assembly 18 connected by a shaft 12, and a high pressure spoolassembly (not numbered) which includes a high pressure compressorassembly 22 and a high pressure turbine assembly 24 connected by a shaft20. A core portion 13 accommodates the high pressure compressor 22 andthe low and high pressure turbine assemblies 18, 24, to define a mainfluid path (not numbered) therethrough. In the main fluid path there isprovided a combustor 26 to generate combustion gases to power the highand low pressure turbine assemblies 24, 18. A mid turbine frame (MTF) 28as part of the core portion 13 is disposed between the high and lowpressure turbine assemblies 24 and 18. The core portion 13 is coaxiallypositioned within the annular bypass duct wall 10 and an annular bypassair passage 30 is defined radially between the annular bypass duct wall10 and the core portion 13 of the engine for directing a bypass air flow32 driven by the fan assembly 14, to pass therethrough.

Referring to FIGS. 1-5, a front mounting assembly 34 is attached to theannular bypass duct wall 10 at a front axial position indicated by line36 (representing a front mounting plane) located close to an inlet (notnumbered) of the annular bypass air passage 30, to mount the engine toan aircraft (not shown). Radial struts 38 are provided near the axiallocation of the front mounting plane 36 and extend between the bypassduct wall 10 and the core portion 13 to support the core portion withinthe bypass duct 10, transferring thrust, lateral and vertical loads tothe front mounting assembly 34.

A rear mounting assembly 40 is also attached to the annular bypass ductwall 10 at a rear axial position indicated by line 42 (representing arear mounting plane), close to an outlet (not numbered) of the bypassair passage 30. The rear mounting assembly 40 includes a plurality ofcircumferentially spaced apart connecting brackets 44 which are attachedto the bypass duct wall 10, and a plurality of link rods 46 havingopposed inner and outer ends (not numbered), extending across theannular bypass air passage 30, and substantially tangential to the coreportion 13 of the engine. Each link rod 46 is connected at the outer endthereof to the bypass duct wall 10 by means of connecting brackets 44and is attached at the inner end thereof to the MTF 28 of the coreportion 13.

The link rods 46 include a first group in which each rod 46 a extendsfrom the outer end to the inner end thereof in a substantiallytangential direction to the core portion 13 corresponding to a firstcircumferential direction 48 a, and a second group in which each linkrod 46 b extends from the outer end to the inner end thereof in asubstantially tangential direction to the core portion 13 correspondingto a second circumferential direction 48 b opposite to the firstcircumferential direction 48 a.

Each of the connecting brackets 44 according to this embodiment, isconnected with two adjacent link rods 46, i.e. one link rod 46 a in thefirst group and the other link rod 46 b in the second group. Inparticular, the connecting bracket 44 has a generally U-shapedcross-section formed by two spaced apart side walls (not numbered)interconnected by a bottom wall 50 which is curved to match theconfiguration of a portion of a peripheral surface of the annular bypassduct wall 10. The connecting bracket 44 is mounted to the outer side ofthe bypass duct wall 10, and is axially positioned between and affixedto two axially spaced apart flanges 52 which extend radially andoutwardly from the annular bypass duct wall 10. At least one of theconnecting brackets 44 includes a mounting portion 54 with one or moremounting openings (not numbered) defined therein, extending radially andoutwardly from the annular bypass duct wall 10 for connection with amounting device of the aircraft (not shown), two of the four connectingbrackets 44 have the mounting portions as shown in FIG. 2. A cavity 56with a closed top and open bottom is provided at the middle of each ofthe connecting brackets 44, defined between the axially spaced apartside walls of the connecting brackets 44 and between twocircumferentially spaced apart end walls 58. The two circumferentiallyspaced apart end walls 58 extend divergently from each other,substantially in the tangential directions corresponding to those of thetwo adjacent link rods 46 (one rod 46 a and the other rod 46 b) whichare connected to the said connecting bracket 44.

The tangential link rods 46 form a short circuit across the annularbypass air passage 30 to transfer the core portion relatedinertia-induced loads from the MTF 28 to the connecting brackets 44 andthe bypass duct wall 10.

The link rods 46 function as an effective load path to the rear mountingassembly 40 for inertia-induced loads originating from the core portion13, thus reducing core deflections from that source (inertia-inducedmeaning loads from gravity or acceleration). The core portion 13 istherefore supported at both mount planes represented by lines 36, 42,rather than the “cantilever” mount of FIG. 9 which does not support thecore portion 13 at the rear and hence causes core droop effect.

It should be noted that if only engine thrust is applied to thestructure of an engine which is of a rear core mount as shown in FIG.10, the center of the bypass would shift laterally from the center ofthe engine core. This is because the core is bending like a simplysupported beam and has a certain amount of bending rotation at the frontmount. This rotation is then carried through to the bypass flange at theoutside of the intermediate case and gives a slope to the bypassrelative to the core, which in turn leads to a lateral shifting ofbypass center relative to the core center at the rear mount. Incontrast, the rear mounting assembly 40 of this embodiment adds in thelink rods 46, and moves the rear mount reaction point to the bypass ductwall 10. This relative centerline shift associated with the rear coremount of FIG. 10, is largely prevented by the tie-up with the link rods46. The bypass duct wall 10 is a stiffer load path than the core portion13, and thus the bypass duct wall 10 rather than the core portion 13,carries the bulk of the moment produced by the rear mount reaction,thereby reducing carcass bending of the core portion 13.

A plurality of openings 60 in the annular bypass duct wall 10 areprovided aligning with the cavities 56 of the respective connectingbrackets 44, in order to allow the outer end of each link rod 46 toaccess the cavity 56 in the connecting bracket 44 mounted to the outsideof the bypass duct wall 10, from the inside of the bypass air passage30. The inner ends of the two adjacent link rods 46 are secured to thecircumferentially spaced end walls 58 of each connecting bracket 44 bymeans of screw fasteners (not numbered), respectively.

Each of the link rods 46 may have an aerodynamic profile incross-section (see FIG. 5), defined with side surfaces 62 extendingbetween a leading edge 64 and a trailing edge 66 with respect to thebypass air passage 30 of the engine. The cross-sectional profile of thelink rod 46 may have a dimension “C” between the side surfaces 62smaller than a dimension “X” between the leading and trailing edges 64,66 in order to reduce air pressure loss in the bypass air flow 32 causedby the link rods 46. A hollow configuration of the link rod 46 may alsobe an option.

The tangential link rods 46 may be connected at their inner endsdirectly to the MTF 28 or by means of any type of connector assemblies.For example, the link rods 46 are usually fabricated in a same lengthfor manufacturing economy and installation mistake-proofing. Therefore,an additional adjustability feature may be required to accommodate theeccentric condition of the bypass duct wall 10 and the MTF 28 of thecore portion 13 caused by manufacturing and assembly tolerances thereof.Therefore, the tangential link rods 46 may be connected to the MTF 28 bymeans of a lockable adjustment device 68 which is able to maintain thelink rod 46 in the correct orientation to the flow.

Referring to FIGS. 1-2 and 5-7 b, the lockable adjusting device 68includes at least one pin 70 and a connecting base 72 to connect atleast one link rod 46 to the MTF 28. In the embodiment shown in FIGS. 2and 6, two pins 70 are provided to each connecting base 72 such thateach connecting base 72 can connect two adjacent link rods 46 to the MTF28 (one rod 46 a and the other rod 46 b). For convenience and precisionof description, only one pin 70 and its connection to the connectingbase 72 is described. It should be noted that the other pin 70 and itsconnection to the same connecting base 72 is substantially the same.

The connecting bases 72 are circumferentially spaced apart and attachedto the core portion 13, for example to a flange 74 radially andoutwardly extending from the MTF 28 of the core portion 13. Each of theconnecting bases 72 defines two holes 76 extending substantiallyradially therethrough. The pin 70 includes a connecting section 78 witha central axis 80 and a base section 82 with a central axis 84. Thecentral axis 80 of the connecting section 78 is eccentric to the centralaxis 84 of the base section 82, at an eccentric distance “d”. Theconnecting section 78 is received in a hole 86 of a link rod 46 (FIG. 7b), and the base section 82 is received in one of the holes 76 definedin the connecting base 72 (FIG. 6). Therefore, an angular position “A”of the eccentric distance d with respect to a direction represented byline 88 which is parallel to the connected link rod 46, may be selectedby rotating the pin 70 before the pin 70 is locked in position to securethe rod 46 to the connecting base 72. When the angular position A of theeccentric distance d changes within 180 degrees, a link length “L” whichis measured in the direction of line 88 (or in the direction of theconnected link rod 46) will change in a range of d×2.

The base section 82 of the pin 70 and the hole 76 defined in theconnecting base 72, may be tapered complimentarily to each other. Thepin 70 may further have a threaded section 90 extending from the smallend of the tapered base section 82, for engagement with a locking nut 92such that the tapered base section 82 of the pin 70 is secured withinthe tapered hole 76 of the connecting base 72 to lock the selectedangular position of the pin 70 when the locking nut 92 is tightlyengaged with the threaded section 90. The base section 82 of the pin 70and the hole 76 of the connecting base 72 may be tapered in an anglesmaller than a self locking tapering angle such that the eccentric pin70 is self-locked with the connecting base 72 against the rotationresulting from offset loads (torque) introduced by the link rods 46 evenif the locking nut 92 accidentally loosens from engagement with thethreaded section 90.

The connecting section 78 may further have a threaded end portion (notnumbered) for engagement with a second locking nut 94 with a washer (notnumbered) to prevent the connected link rod 46 from disconnecting fromthe connecting section 78 of the pin 70.

The pin 70 may further define a hexagonal recess (not numbered) definedin the end of the connecting section 78 as a means to rotate and holdthe pin to maintain the selected angular position of the pin 70 whiletightening the nut 92. The lockable adjustment device 68 provides acompact configuration to ensure the concentricity of the bypass ductwall 10 and the MTF 28. This compact configuration can be convenientlyattached to the MTF 28 and located outside of the annular bypass airduct 30. The adjustment of the eccentric pin 70 does not affect theorientation of the aerodynamic profile of the link rods 46 in the bypassair flow 24. The self-locking tapering feature of the eccentric pin 70provides a level of mistake-proofing in the field. Furthermore, there isno need to re-adjust the pins 70 once the engine is assembled, and thelink rods 46 may be freely removed and re-installed in the field formaintenance purposes because the connecting base 72 which receives therespective link rods 46 is independently affixed to the MTF flange 74,thereby maintaining the adjustment.

FIG. 8 shows a lockable adjustment device 68 a according to anotherembodiment in which similar components and features are indicated bynumerals similar to those used for the lockable adjustment device 68 ofFIG. 6 for ease of description. The difference between devices 68 ofFIG. 6 and 68 a of FIG. 8, lies in that the pin 70 of adjustment device68 a further includes an extension 96 extending from the connectingsection and is concentric with the base section 82. The extension 96 isreceived in a hole 97 defined in a supporting member such as a plate 98.After the pin 70 is locked in its adjusted position in the connectingbase 72 and an inner end of a link rod 46 is attached to the connectingsection 78 of the pin 70 (similar to that shown in FIG. 7 b), the plate98 is attached to the extension 96 of the pin 70 by receiving theextension 96 to extend through the hole 97 therein. The plate 98 is thenaffixed by fasteners (not shown) to the connecting base 72 or to the MTF28. The extension 96 may optionally have a threaded end portion 100 suchthat the locking nut 94 with a bushing (not numbered), may be used tofurther secure the plate 98 to the pin 70. The lockable adjustmentdevice 68 a provides the connecting base 72 and plate 98 as two spacedapart support elements flanking the connecting section 78 which connectsthe link rod 46, thereby forming a double-shear version of an adjustablepin connecting arrangement, in contrast to the device 68 of FIG. 6 whichis a single-shear version of an adjustable pin connecting arrangement.

It should be understood that a support-link lockable adjustmentarrangement as illustrated by devices 68 or 68 a is described as a partof a support link of a mounting system for a long duct mixed flow (LDMF)turbofan gas turbine engine in the above-described embodiments. Howeverthis support-link lockable adjustment arrangement may be applicable tosupport links of other types for interconnecting an annular outer caseand an annular inner case of a gas turbine engine. This compact cam-typeof support-link lockable adjustment arrangement can be used at eitherend of the link in its attachment to an outer case or an inner case,conveniently located outside of the annular bypass air duct. Thissupport-link lockable adjustment arrangement may be used with tangentiallinks as described in this application, or with radial support links.The eccentric pin may extend either in a substantially radial directionas described in the embodiments or may extend in a substantially axialdirection.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without departing from the scope of the concept disclosed. Forexample, the short circuit for transferring inertia-induced loadsdirectly from the MTF to the bypass duct casing may be configureddifferently from the particular embodiments described above and may beapplicable to any bypass duct gas turbine engine different from theengine as described. The mounting assembly incorporated with theconnector for connecting the link rods to the bypass duct wall may beconfigured differently form the described embodiments of the connectingbrackets. Still other modifications which fall within the scope ofdescribed concept will be apparent to those skilled in the art, in lightof a review of this disclosure, and such modifications are intended tofall within the appended claims.

What is claimed is:
 1. A support-link having lockable adjustmentfeatures for interconnecting an annular outer case and an annular innercase of a gas turbine engine, the annular inner case being co-axiallypositioned within the annular outer case, the support link comprising: aplurality of rods having opposed inner and outer ends, each rod beingconnected at the outer end to the annular outer case and connected atthe inner end to the annular inner case, the rods extendingsubstantially tangentially across an annulus defined radially betweenthe outer and inner cases; and a plurality of lockable adjusting devicesfor adjustably connecting the respective rods to one of the annularouter and inner cases, each of the lockable adjusting devices includinga pin and a connecting base attached to said one of the outer and innercases, each of the pins extending in a substantially radial directionand having a connecting section and a base section, the connectingsection having a central axis eccentric to a central axis of the basesection, the connecting section being received in a hole defined in oneof the outer and inner ends of one rod and the base section beingreceived in a hole defined in the connecting base, the pin beingrotatable relative to the respective rod and connecting base in order toselect an angular position of an eccentric distance between the centralaxes of the respective connecting section and base section of the pinbefore the pin is locked in position to secure the rod to the connectingbase wherein the connecting bases of the respective lockable adjustingdevices are circumferentially spaced apart, each of the connecting basesconnecting two adjacent rods.
 2. The support link as defined in claim 1wherein the base section of the pin and the hole defined in theconnecting base of the lockable adjusting device, are taperedcomplimentarily to each other.
 3. The support link as defined in claim 2wherein the base section of the pin and the hole defined in theconnecting base are tapered in an angle smaller than a self-lockingtapering angle.
 4. The support link as defined in claim 2 wherein thepin comprises a threaded section extending from a small end of thetapered base section of the pin for engagement with a first locking nutto lock the tapered base section of the pin in the tapered hole of theconnecting base.
 5. The support link as defined in claim 4 wherein theconnecting section of the pin comprises a threaded end portion forengagement with a second locking nut to prevent the rod fromdisconnecting from the connecting section of the pin.
 6. The supportlink as defined in claim 4 wherein the pin comprises an extensionextending from the connecting section and being concentric with thetapered base section, the extension being received in a hole defined ina supporting member, the supporting member being attached to one of theconnecting base and the inner case.
 7. The support link as defined inclaim 6 wherein of the extension of the pin comprises a threaded endportion for engagement with a second locking nut.
 8. The support link asdefined in claim 1 wherein the lockable adjusting devices are providedto connect the inner ends of the respective rods to the inner case. 9.The support link as defined in claim 8 wherein the rods extendsubstantially tangentially across an annulus defined radially betweenthe outer and inner cases.